1. Technical Field
The present invention relates to a semiconductor integrated circuit, and more particularly, to a circuit (hereinafter, referred to as an “E-fuse detection circuit”) in a semiconductor apparatus for cutting an electric fuse of a semiconductor integrated circuit and detecting whether the electric fuse is cut or not.
2. Related Art
In a semiconductor integrated circuit, fuses are employed to repair a failed cell, store a chip identification, and supply various mode signals into the semiconductor apparatus.
Fuses can be categorized into a laser blowing type and an electrical blowing type.
Since adjoining fuse lines are likely to be influenced by irradiation of laser beams in blown type fuses by laser beams, it is required that the fuses are separated from one another at least by a predetermined distance. Thus, in highly integrated semiconductor circuit, layout efficiency may be decreased.
In electrical blowing type fuses, on the other hand, a programming current is applied to a fuse link such that the fuse link is blown through an EM (electromigration) effect and Joule heating. Such electrical blowing type fuses can be used even after a package level and are referred to as electric fuses.
The electric fuses can further classified as an anti-fuse and an E-fuse types.
An anti-fuse is configured in a transistor type. In an anti-fuse, a high voltage is applied to a gate electrode and a substrate such that a gate oxide layer is ruptured.
An E-fuse is configured in a capacitor type. In an E-fuse, a large current is applied between both electrodes such that a capacitor is oxide layer is ruptured.
FIG. 1 is a diagram illustrating a conventional fuse circuit.
Referring to FIG. 1, an E-fuse circuit 10 includes an E-fuse F, a switching transistor 20 and an amplification unit 30.
The E-fuse F and the switching transistor 20 are electrically connected with each other and are coupled between first and second voltage sources VpowerH and VpowerL. The amplification unit 30 is coupled to a coupling node between the E-fuse F and the switching transistor 20.
If a cutting signal A is inputted to the switching transistor 20, a high current is applied to the E-fuse F and the switching transistor 20 by the voltage of the first voltage source VpowerH which has a voltage level capable of rupturing the E-fuse F. As a consequence, the E-fuse F is ruptured.
Therefore, in order to rupture the E-fuse F, a predetermined high current is needed. For example, when assuming that the resistance of the E-fuse F is R1 and the resistance of the switching transistor 20 is R2, a current I for rupturing the E-fuse F is expressed as in the following Mathematical Equation 1.
                    I        =                                                            V                power                            ⁢              H                        -                                          V                power                            ⁢              L                                                          R              ⁢                                                          ⁢              1                        +                          R              ⁢                                                          ⁢              2                                                          [                  Mathematical          ⁢                                          ⁢          Equation          ⁢                                          ⁢          1                ]            
Here, since the E-fuse F generally includes a metal pattern, the resistance value of the E-fuse F is substantially low. Hence, in order to secure a high current I greater than a predetermined value, the level of the first voltage source VpowerH should be raised so that a current can be increased, or the area of the switching transistor 20 should be increased so that a low resistance can be acquired.
However, in currently used memory apparatuses, it is substantially difficult to raise the level of the first voltage source VpowerH over the level of a pumping voltage VPP.
Also, it is substantially difficult to increase the area of the switching transistor 20 beyond a predetermined range within a limited space.